1. Field of the Invention
The present invention relates to wooden material where wood elements are bonded together with a binder resin, and in particular to a wooden material with good resistance to water absorption, resistance to moisture, and dimensional stability, and with excellent strength, and to a manufacturing method therefor.
This application is based on patent application No. Hei 10-343468 filed in Japan, the content of which is incorporated herein by reference.
2. Description of the Related Art
Heretofore, manufacture of wooden material has been carried out by bonding together with a binder resin, wood elements in various forms such as board, particles, chips, fibers, or powder. However with wooden material manufactured in this manner there is a problem of dimensional deviations due to high hygroscopicity, and poor water resistance and moisture resistance.
As a method for solving this problem, a method where the wood elements are subjected to acetylation processing and then bonded into an integral unit with a binder resin has been disclosed in Japanese Patent Application, First Publication Nos. 5-269710, and 7-9411. When as disclosed in these publications, the wood elements are subjected to acetylation processing, absorbency, and hygroscopicity are reduced, and consequently dimensional stability is improved.
However, wooden materials made using wood elements, which have been subjected to acetylation processing, have the defect that the strength is lower compared to wooden material made from wood elements which have not been subjected to acetylation processing.
In particular, with fiberboard made using wood fibers as the wood elements, the drop in bending strength due to acetylation is comparatively large. For example the bending strength measured in accordance with JIS A 5908, of fiberboard made by bonding wood fibers (trade name F-4-17, manufactured by Canadian Forest Products Ltd. of Canada) using denatured melamine (15% of the wood fibers) was approximately 34 MPa for the case with no acetylation processing of the wood fibers, compared to approximately 16 MPa for the case with acetylation processing of the wood fibers.
One reason for this drop in strength is considered to be due to a drop in adhesion of the wood fibers with binder resins such as urea, melamine, phenol, urethane, due to the acetylation. Furthermore, it was also considered difficult to have a rock hard layer of high density and high rigidity for the surface layer of the fiberboard.
Accordingly, it is an object of present invention to provide a wooden material having excellent resistance to water absorption and resistance to moisture, good dimensional stability, as well as excellent strength.
In order to solve the above problems, the wooden material of the present invention comprises ozonized wood elements and binder resin bonding said ozonized wood elements together, wherein said ozonized wood elements are made by acetylating wood elements and then subjecting the acetylated wood elements to an oxidization treatment using ozone.
With the present invention, resistance to water absorption and resistance to moisture are excellent and hence dimensional stability is good. Moreover the adhesiveness between the wood element and the binder resin is improved and a rock hard base layer is formed on the front and rear surfaces, thus giving a wooden material with excellent strength.